System of control



R. E. HELLMUND.

SYSTEM OF CONTROL.

APPLICATION mzn MAR.28,1917.

4 SHEETS-SHEET 1.

Patented Oct. 28,

Tral/e y 2.6!

lllllm INVENTOR Rudolf E Hell/ 70nd WITNESSES:

" A'nbRuEY I R. E. HELLMUND. SYSTEM OF CONTROL. APPLICATION FIEED MAR. 28,1917- 1,320,055. Patented Oct. 28,1919.

4 SHEETS-SHEET 2.

Fig. 3.

124 *!64 151 5 Isa-f 5 /70 On Off Trolley Ground 7 Trolley 7 Al J42 WITNESSES: Ground lNVENTOR {MA 4 M fiuago lf 5 Hal/mund M ATTORNEY R. E. HELLMUND.

SYSTEM OF CONTROL.

APPLICATION FILED MAR. 28, sen.

1 320,055. Patented Oct. 28, 1919.

. 4 SHEETS-SHEET 3.

Trolley Fig. 5.

ZOE/raver:

Ground;

/ Tro/Iey WITNESSES: 6raund INVENTOR Zldfl M. fludgf [He/Imund NW 7 ATTbRNEY UNITED TE PATENT OFFICE-.-

Y mmonr E. HELLMUN'D, or swissvnnn, rnunsxnvnrm, AssIGNon. ro'wnsrnmnousn ELECTRIC & nannrnornitme comrm, A conronxrxon or PENNSYLVANIA.

To all whomitma concern: I

-Be it known t at I, RUDOLF E. HELL- MUND, a subject of the Em eror of Germany, and a resident of Swissvale, in] the county of Allegheny and StateofPennsylvania have invented a new and useful Improvement in Systems of Control, of which the following is a specification.

My invention relates to systems of control and especially to thecontrol of electric railway. motors and the like during regenerative braking periods.

In order to brake a momentum-driven vehicle down a ads, with a maximum de e of safety, it 1s desirable to im art a rat er flat speed-torque curve tot e regenerating machines, that is, a slight increase in speed of the vehicle should be accompanied by a relatively greatincrease of torque or braking effort, whereby the vehicle will be away. However,

prevented from running inasmuch as such flat operating'characteristicmay be accompanied by relatively heavy currents and sudden variations thereof that render the machines liable to flashover difiiculties by reason of field-flux dis]- tortion and high voltage between commuta-' speedv are lnherently prevented. Furthermore, in circumstances where the momentum-driven machine is operated in accordance with a fiat curve other arran ements should be provided to insure an even distribution of load between the several machines. V y

One object of my present invention is to provide a system of the above-indicated character, wherein a predetermined com:

poundingefi'ect is imparted to the machines individually, and a difierent type and degree of compounding efl'ect is imparted to a the machines jointly.

More specifically stated, it is an object of my invention to provide an exciter system for momentum-driven mam dynamo-electric machines embodying means for imparting a negative compounding effect to t e matem to be employed in connection wit I an operatin sYs'rnm or CONTROL. I

implication of Letters Patent." Patented Oct. 28, 1919. Application and March 28. 1917; Serial no. 157.918. i

chines individually. and a lesser ositive compoundin efl'ectto the machines Jointly; that is, the individual machines tend to of)- erate in accordance with a relatively steep characteristic curve, whereas the joint or combined operation of the machines is represented by a relatively flat curve. My invention may'best be understood by reference to" the accompanyin drawin disclosing various systems em dying 5 principles of my present invention to a greater or less degree, and wherein Figure 1 1s a diagrammatic view of a set of main circuits andauxiliary-machine circuits embodying my inv ention, together with certain governln circuits for the machines; Figs 2 1s' a simi ar view of a modified system corresponding to Fig. 1; Fig. '3 is a diagram: matic view. of an auxiliary governin s s- 2; and Fig. .4 to Fig. 11, inclusive," are simplified dia ammatic views of main-machine' circuits and auxiliary-machine circuits constituting modifications of the present invention.

. Referring to Fig. 1, the systemshown comprlses supply-circuit conductors, res ec- -ti.v,ely marked Trolley and Ground; a

plurality of main dynamo-electric machines res ectively having 'armatures A1. and A2 an "field windings F1 and F2 of the series type; main-circu t. stabilizing resistors R1 and R2 that are associated w1th the respective machinesin a manner'to described; an aux1l1ary' motor-generator set 1 that is driven from the supply circuit and is connected to excite the main field windings during'the regenerative period; a relay device 2 of the motor typefor, govermnga controller 3 that is adapted to vary certain circuit connections of the motor-generator set 1 and the relay 2through the agency of is mechanically connected with an exciting or auxiliary gsnerator armature 11 by means ofa sha 12, or otherwise; a seriesrelated field winding 13 for the drivin armature 10; a regeneratedmurrent-excite mechanism 4; and a master field winding 14 for the exciting armature 11 and a second variable field winding 15 therefor that is-connected in series-circuit relation with the driving motor armature and field winding.

The relay device 2 comprises an oscillatable armature '16 which may be variably energized from the supply circuit and upon the shaft 17 of which an auxiliary switching device or drum controller 18 is mounted to carry a contact member 19 that is adapted to bridge a plurality of stationary control fingers 20, 20b and 200 when the relay device occupies certain of its positions, a, b and 0, corresponding to positions a, Z) and c of the master controller MCI. A suitable spring 21 or its equivalent, is pro vided to normally hold the relay device in the illustrated position, b, in accordance with a familiar practice. An exciting field winding 22 for the relay device is energized from a resistor 23 connected in the mainarmature or regenerative circuit. The relay device 2 is thus responsive to variations of regenerated current, while the operation thereof may also be adjusted through the actuation of the controller 3 to vary a resistor 25 by means of control fingers 26 connected to various points thereof and .successively engaged by a contact segment 27 as the controller 3 moves through its successive positions. It will be understood, however, that the relay device 2 may be actuated in accordance with variations of main-machine torque, if desired, by connecting its field winding 22 across a port-ion of one of the main-circuit resistors R1 and R2 which, as subsequently pointed out, carry the sum of the corresponding main-armature and main-field-winding currents, such sum being approximately proportional to the product thereof over a certain range and, therefore, to the machine torque.

A torque-relay action may also be obtained by connecting the relay armature 16 across either main field Winding, and employing the illustrated connections for the relay field winding 22.

In addition to the control fingers 26 and contact segment 27 of the controller 3 that are associated with the auxiliary-circuit resistor 25, a second series of control fingers 28 may be connected to selected points of the field winding 15 for the exciting armature 11, and a contact segment 29 of suitable configuration is provided for successively engaging the control fingers 28 in the desired sequence.

The operating mechanism 4 for the controller 3 is of a familiar electrically-controlled, pneumatically-actuated type and comprises a pinion 30 which is rigidly secured to one end of the operating shaft 31 of the controller and is adapted to mesh with a horizontally-movable rack member 32, the

and conductors 47 and 48 to opposite ends of which constitute pistons 33 and 34 that travel within suitable operating cylinders 35 and 36, respectively. A normally closed valve 37 is associated with the outer end of the cylinder 35, and a normally open valve 38 communicates with the outer end of the other cylinder, fluid pressure being admitted to the respective valves through ipes or passages 39 and 40 from any suitable source (not shown). The valve 37 is provided with an actuating coil On for opening the valve when the coil is energized, and the other valve 38 is provided with a similar actuating coil Off which,

when energized, closes the valve and effects communication of the cylinder 36 with the atmosphere.

The mechanical operation of the operatin device 4, without regard to the electrical connections effected thereby, may be set forth as follows: By reason of the normally open condition of the valve 38, the pistons 33 and 34 are biased to the position shown, and the controller 3 occujh'es its off position. By concurrently energizing the coils On and Off, the normal fluid-pressure conditions in the mechanism are reversed, that is, fluid pressure is admitted to the cylinder 35 and is exhausted from the cylinder 36, whereby a movement of the pistons toward the right ensues, accompanied by a corresponding movement of the controller 3 through its operative positions.

To arrest such movement at anytime, it is merely necessary to de'energize the off coil, whereby fluid pressure conditions in the mechanism are balanced and a positive and reliable stoppage thereof is effected. To produce a return movement of the mechanism, the actuating coils are concurrently deenergized, whereby fluid-pressure con ditions revert to the original state and the apparatus is returned to the illustrated position.

For the sake of simplicity and clearness, I have omitted from the drawing various main and auxiliary-circuit switches and have shown themaster controller M01 as governing only the actuating coils of the operating mechanism 4. It will be understood that regenerative operation may be inaugurated in any well-known manner, which need not be discussed here. Assuming, therefore, that the master controller M01 has been moved to its final operative position a, a circuit is completed from the positive terminal of a battery B, or other suitable source of energy, through conductor 42, control fingers 43 and 44which are bridged by contact segment 45 of the master controller-conductor 46, actuating coil On, the opposite battery terminal. Another circuit is com pleted from the contact segment 45 of the master controller through control finger 50,

conductor 51, actuating coil Off and conductor 52 to negative conductor 48.

Since both actuating coils ofthe operating mechanism 4 are concurrently energized,

1 roller may be moved backwardly to its intermediate position 1), whereby the contact segment 45 becomes disengaged from the control finger 50 to thus de'e'ner-gize the 011" coil and effect the stoppage of the mechanism, as previously setforth.

The main regenerative circuit is completed from the trolley through conductor 55, where the circuit divides, one branch including conductor 56, main armature A1, junction-point 57 and the main-circuit resistor R1 to junction-point 58, and the other branch including conductor 59, main armature A2, junction-point 60 and the main-circuit resistor R2 to junction-point 58, whence a commoncircuit is continued through conductor 61, field winding 14 for the exciting armature 11 and conductors 62, 63 and 64 to the negative supply-circuit conductor Ground.

The main field winding circuit is established from the positive terminal of the exciting armature 11 through conductors 67, 68 and 62, field winding 14 for the exciting armature 11, conductor 61 to junction-point 58, where thecircuit divides, one branch including main-circuit resistor R1, main field winding F1 and conductor 69 to junctionpoint 70, and the other branch including main-circuit resistor R2 and main field winding F2 to junction-point 70, whence a common circuit is completed through conductor 71 to the negative terminal of the exciting armature.

An auxiliary circuit is completed from the positively energized conductor 59 through conductor 72, auxiliary motorcarmature 10 and field winding 13 thereof, conductor 73, control fingers 28 and contact segment 29 of the controller 3 and thence, through a certain portion of the field winding 15 for the excitlng armature 11 and conductor 68, to the negative conductor 63.

.A further auxiliary circuit is established from the positively-energized conductor 56 through conductor 75, cooperating control fingers 26 and contact segment 27 which are associated with the resistor 25-, conductor 76, the armature 16 of the relay device 2 and conductors 77 and 64 to ground. Since the armature of the relay device is energized through the circuit just traced, and the field winding 22 therefor is energized in accordance with the regenerated current. as previously mentioned,the relay device is operative to vary the governed circuit connections in accordance with variations of mainarmature or regenerated current.

The operation of the main-circuit resistors R1 and R2 for inherently imparting to the machines individually a relatively steep or negative compound characteristic will now be described. Assuming an incipient increase of regenerated current in the main armature A1, for example, the correspondingly increased voltage drop across the resistor R1 immediately effects a reduc- 'tion of the voltage that is available for delivery from the exciting armature 11to the main field winding F1, since the resistor R1 is also in circuit with the main field winding F1 andthe exciting armature 11. The converse action takes place in case of an incipient decrease of regenerated current. Thus, the resistors R1 and R2 tend to inherently maintain a substantially constant mainarmature or regenerated current, by reason of the'fact that the main-field-winding current is automatically varied oppositely or negatively with respect to the main-armature current variations. As will be understood, by suitable design and proportion of parts, the steepness of the o crating characteristic im arted to the in ividual machines by the resistors R1 and R2 may be selected to best meet operating requirements. The regenerative connections just described form no part of my present invention except in so far as they perform a certain necessary function incooperation therewith, and are fully set forth and claimed in my co-pend- 100.

ing application, Serial No. 44,443, filed Aug.

' 9, 1915,.patented April 1, 1919, No. 1,298,706.

the machines jointly by reasonof the employment of the regenerated-current-excited field winding 14 for the exciting armature 11, whereby the delivered voltage thereof tends to increase or decrease with variations of regenerated current. Thus, by suitably designing the auxiliary field winding 14, the positive compound eflt'ect thereof upon the motors jointly may be selected to cause the machines to operate, as a unit, in accordance with a"relative1y flat operating characteristic of the type previously described.

The automatic control of the system by 12 the relay device 2 when the master controller MCI occupies its neutral or holding position b, will now be described. In general, movement of the relay device to the one or the other of its outer positions, a and 0', respectively effects a backward and a forward movement of the controller 3.

There is danger-of the occurrence of excessive regenerated currents, corresponding, for instance, to the slipping-point of the vehicle wheels, when the machines are 0 erating in accordance With such a at curve, especially in case of a sudden material variation of supply-circuit voltage, which may also lead to flash-over difiicul- .ties. Under such heav -current conditions, the increased torque o the relay armature 16, by reason of the increased energization of the corresponding field winding 22, overcomes the opposing action of the spring 21 and actuates the drum controller 18 into position a, whereby the control fingers 20b and 200, which are respectively connected.

to the conductors 46 and 51, are disengaged from the contact segment 19, thereby de- -energizing both the off and the on coils,

provided the master controller occupies its position b, to cause a backward movement of the controller 3, in accordance with prev'iously-described principles, until conditions in the various machine circuits are adjusted to conform to the new supply-circuit conditions. In the present case, such backthe relay device 2 is of a lower value t an tive circuit resistance of the resistor 25.

Thus, for the initial operative positions of the controller 3, which correspond to highspeed regenerative operation, the settin of during subsequent main-machine operation; that is, the initial regenerative current is ke t relativel lowin value.

nder pre etermined low-current conditions, the spring 21 overcomes the torque of the relay armature 16 to effect the actuation of the relay device to position 0, whereby the actuating coils On and Off are reenergized to produce forward movement of the controller 3. Thus, the regenerated current is maintained by the relay device 2 within predetermined limits.

Furthermore, when the above-mentioned flat speed-torque characteristic is utilized, there is a possibility that, upon a sudden increase of the track grade, the' machines may begin to accelerate and consume relatively heavy motor currents, with consequent danger of flash-over condltions. Whenever such reversed-current actlon occurs, the rlay device 2 is adapted to eflect the actuation of the drum controller 18 tothe position 0, whereby the actuating coils On and Oil are both energized and forture reactive effect.

ward movement of the controller 3 ensues until conditions are again suitable to produce regenerative operation. Thus, the momentum-driven machines will always exert a braking effect while the master controller occupies its braking positions, until the controller 3 has reached its-final position, wherein the voltage of the exciting armature 11 attains its maximum value and a relatively high degree of saturation of the main field windings is obtained. Under such conditions, reversal of the main-machine current is not injurious and, therefore, no further protection of the system in this respect is necessary.

Since the'com ounding effect of the re sistors R1 and E2 is practically instantaneous in its action, and the opposmg effect of the auxiliary field winding 14 operates with a slight time element, the rise of regenerated current in any case will be sufiiciently tardy to permit the regulating operation of the relay device 2 before dangerous currents are obtained.

Referring to Fig. 2, the system shown comprises the and the main dynamo-electric machines, as set forth in connection with Fig. 1 and, in addition, an exciting motor-generator set a plurality of motor-type relay devices 81'and 82 for maintaining the regenerated current within, predetermined limits; a plurality ofsolenoid-type relay devices 83, 84 and 85 for governin the s stem operation under conditions 0 a sud en interruption of supply-circuit voltage; a controller 86 that is operated by the mechanism 4 for varying the active circuit values of the main-c1rcuit resistors R1 and R2; and a master controller M02 that is adapted to occupy a plurality of operative positions a to c, inclusive, for adjustin the operation of the motor-type relay devices 81 and 82.

The main circuit resistors R1 and R2 serve the same function as that set forth in connection with Fig. 1, and their negative compounding effect upon the motors individually is counterbalanced to' the desired degree by designing the exciting armature 11 with a drooping voltage-current characteristic, that is, a rapid decrease of voltage is produced upon an increase of current, within a predetermined ran Such a result may be obtained by a shifting of the brushes 90 and 91 of the exciting armature 11 by means of a suitable actuating device 92 to such an extent and in such a direction as to suitably increase the arma- The exciting machine is also preferably provided with a damper winding that is located in the polar facesof the machine, in accordance with a. familiar practice, to render the voltage chan es of the armature relatively slow or sluggis and thus provide an appreciable time element supply-circuit conductors other relay device 81.

' circuit and the relay occupies the illus-.

in such changes to allow for relay operation, for instance; For the sake of simplicity and clearness, such damper winding is here conventionally shown by a shortcircuited coil 93.

The motor-type relay device 81 is provided with an oscillatable armature 95, upon the shaft 96 of which a switching device or drum controller 97 is mounted to carry a contact segment 98 .that normallybridges a pair of control fin ers 99 for a purpose to be described. A eld winding 100, energized from a predetermined portion of the main-circuit resistor R1. is provided and, since the armature 95 is energized from the main-machine or regenerated voltage, the operation of the relay device 81 occurs in accordance with variations of main-machine torque, as previously pointed out. ,An opposmg spring 21 is trated upper position under conditions of normal regenerative current flow.

The solenoid-type rela devices 84' and 85 are energized from t e supply circuit 9 when the relay device 83 drops to its lower position and have different voltage settings corresponding, for example, to the torque settings of the motor-type relay devices 81 and 82, for maintaining the generated'voltage of the momentum-driven main machines within any desired limits, after aninterruption of supply-circuit voltage when the relay devices-81 and 82 are rendered inoperative, and the generated voltage is thus maintained at a value suitable for recommencing-regenerative operation as soon as the supply-circuit voltage is resumed.

Referring temporarily; to the auxiliary governing circuits shown in Fig. 3, such circuits comprise the actuatin coils On and Ofli' and various auxi iary contact members of the relay devices 81 to 85, inclusive, together with a battery B, or other suitable source of energy, and a governing switch 120.

Assuming that a preliminary regenerative operation obtains, the switch 120 is 'closed to com lete a circuit from one ter minal of the attery B through conductor 121, switch 120, conductor 122, contact member 98which is normally bridged by control fingers 99 of the high-current relay device 8lauxiliary contact members 123 of the relay device 83 in its upper or energized position, conductor 124, where the circuit divides, one branch including the actuating coil On and conductor 125 to junction-point 126, and the other branch includin conductor 128, contact segment 103wh1ch is normally bridged by control fingers 104 of the low-current relay device '82the actuating coil Ofi' and conductor 130 to junction-point 126, whence a common circuit is completed through conductor 131 to-the negative battery terminal.

Under suclr conditions the controller 86 is actuated by its operating mechanism 4 into successive operative positions, the main circuits being established from the trolley through the main armatures A1 and A2 in parallel relation to conductors 135 and 136, respectively, and thence through control fingers 110 and contact segment 111 which are associated with the main-circuit resistor R1 and through control fingers 112 and contact segment 113 which are associated with the main-circuit resistor R2, circuit being continued from the respective resistors through conductors 137 and 138 to a conductor 139, the actuating coil of the relay device 83 and conductor 140 to the ne ative supply-circuit conductor Ground.

he circuits of the auxiliary exciting armature 11, the auxiliary motor armature 10 and their field'windings are substantially the same as set, forth in connection with Fi 1 and need not be traced.

n auxiliary circuit is established from the trolley throughconduetor 142, control fingers 143, which are successively engaged in a predetermined sequence by contact segment 144 of the master controller MG2 to vary a resistor 145, conductor 146, the armature 95 of the'relay device 81, conductor 147, the armature 101 of the relay device 82 and conductor 148 to the negative conductor 139.

A further'auxiliary circuit is completed from the trolley through conductors 150 and 151, the actuating coils of the relaydevices 85 and 84 in series relation, stationary contact members 152, which are bridged by movable contact member 123 of the relay device 83, when occupying itslower or. no-

ground. 7

Whenever the regenerated current decreases to apredetermined lower value, the low-current relay device 82 is biased by the spring 21 to occupy the illustrated position to permit forward movement of the concurrent position, and conductor 154 to troller 86 by completing the energizing circuit of the 011" coil, as previously described, thereby gradually excluding the resistors R1 and R2 from circuit. Under normal current conditions, the torque of the relay armature 101 opens the circuit in question, and the controller 86 is held stationary.

Upon the occurrence of a predetermined relatively heavy regenerated current, the torque of the relay device 81 is sufficiently increased to overcome the opposing action of the spring 21 and actuate the drum controller 97 into such position as to effect the disengagement of the contact segment 98 from the control fingers 99, thereby interrupting the common energizing circuit of the actuating coils' On and 011', as clearly indicated in Fig. 3, to effect a return movement of the controller 86 and thus insertgradua-lly increasing amounts of the resistors R1 and R2 in circuit to'cause a reduction of the regenerated current. When such reduction has taken place, the spring 21 again predominates to actuate the relay device into the illustrated position and permit forward operation of the controller 86.

Thus, 'by suitably adjusting the relay devices 81 and 82, which may be connected through individual master controllers and resistors, if desired, instead of the common master controller M02 and resistor 145, the regenerated current may be automatically maintained between predetermined current or torque limits to best meet operating requirements.

If, for any reason, for example, an interruption of supply-circuit voltage, the regenerated current should decrease to a relatively low value, the relay device 83 dro s to its lower position to interrupt the com hined energizing circuit of the actuating coils On and Off and to close the energizing circuit for the actuating coils of the relay devices 84 and 85 by the bridging of stationary contact members 152 by the movable contact member 123, and a new circuit is thereupon completed from the positively energized conductor 122 (Fig. 3) through conductor 160, cooperating contact members 161 of the high-voltage relay device 84 in its lower or normal position, conductor 162, stationary contact terminals 163 whichrare bridged by contact disk 164 of the no-current relay device 83 in its lower position, conductor 124, where the circuit divides, one branch including the actuating coil On and conductor 125.to junction-point 126, and the other branch including conductors 128 and 165, stationary contact members 166 which are bridged by contact disk 167 of the nocurrent relay device 83 in its lower position, conductor 168, cooperating stationary and movable contact members 169 ofthe lowvoltage relay device 85 when occupying its lower position, conductor 17 0, actuating coil OE and conductor 130 to the junctionpoint 126, whence circuit is completed as already traced.

The relay device 85 drops to its lower or closed position to effect an actuation of the controller 86 toward its final operating position whenever the main-machine generated voltage reaches a certain lower value, While the high-voltage relay device 84 is lifted to its upper or open position to effect circuit voltage and the resultant lifting of the no-current relay device 83 to its illustrated upper position, the control of the system is again invested in the motor-type relay devices 81 and 82, and the solenoidtype relay devices 84 and 85 are rendered inoperative, such transfer of governing con nections being accompanied by no heavycurrent surges, by reason of the above-described regulation of generated voltage.

Referring to Fig. 4, the simplified system shown comprises the main dynamo-electric machine and the main-circuit resistors, as illustrated inFig. 1, as well as the auxiliary armatures 10 and 11 and, in addition, a series compensating field winding 175 for the auxiliary motor armature 10 and a shunt field winding 176 therefor, the excitation of which may be varied by means of a resistor 177 in circuit therewith, and a plurality of field windings 181 and 182 for the exciting armature 11 that are respectively connected in series-circuit relation with the main-circuit resistors R1 and R2.

The exciting armature 11 is thus provided with field fluxes corresponding to the sum of the individual regenerated and fieldwinding currents of the main dynamoelectric machines. In this way, the inductive and resistive effects of the auxiliary field windings 181 and 182 assist the above-described negative compounding eflect of the resistors R1 and R2, and the positive compounding efi'ect of the auxiliary field windings upon the exciting armature 11 relative to the negative efi'ect produced upon the machines individually by the corresponding resistors and auxiliary field windings may be varied to meet any desired requirements, the negative effect preferably slightly predominating, for reasons previously ex plained.

Fig. 5 differs from Fig. 4 only in the substitution of the field winding 14, which is energized by the combined main-armature or total regenerated current, for the field windings 181 and 182 of Fig. 4. The desired relative effects of negative and posi- A desirable combination of circuits comprises the use of the low-current relay device 82 of Fig. 2, with its field winding 105 connected across the field winding 14 of Fig. 5. Such connection would render the action of the relay device very sensitive to changes of regenerated current, by reason of the corresponding inductive effect of the field winding 14. In Fig.6, the main dynamo-electric machines are provided with subdivided field windings F3 and F 1 that are connected in circuit with the non-corresponding armatures A2 and A1, respectively, the remaining circuits being similar to those previously set forth. I

Under conditions of regenerative operation, the main armature or regenerative circuit is established from the trolley where the circuit divides, one branch including conductor 200 main armature Al conductor 201, a predetermined upper and reversely-connected section 202 of the noncorresponding field winding F4 and conductor 203 to the main-circuit resistor R2, and a second branch including conductor 204, main armature A2, conductor 205, a predetermined upper and reversed section 206 of the non-corresponding field windin F3 and conductor 207 to the main-circult resistor R1. In the present instance, the resistors R1 and R2 are connected in parallel relation and may, therefore, be supplanted by a single equivalent resistor. A common circuit is completed from junctionpoint 208- of the resistors throughconductor 209 to ground. The main-circuit resistors Rl and R2 inherently impartthe above-mentioned negative compounding characteristic to the se-' ries related main armatures individually and such compounding effect is counteracted to any desired degree by the proper provision of ampere-turns corresponding to the regenerated current flowing in a posltive or aiding direction, with respect to inain-arma ture voltage, as indicated by the arrows, through the reversed main-field-winding sections 202 and 206 which, consequently, act cumulatively with respect to the principal portions of the main field windings andthe positive compounding efi'ect thereof.

The final result may be predetermined by suitable arrangement of parts to produce the desired imparting of a relatively flat speed-torque curve to the main machines ointly. Furthermore, the interconnection of non corresponding main armatures and field windings tends to automatically bal ance or distribute the load between the main. machines since, for example, if the current traversing the main armature A1 increases, the increased flux emittedby reversed section 202 of the non-corresponding field'winding F4 will cause an increase of voltage and, therefore, ofcurrent in the other or corresponding main armature A2.

In Fig. 7, a somewhat similar system is illustrated, wherein the circuit connections are simplified to a certain extent and, in particular, the system is better adapted for use with the well-known standard fieldcontrol type of railway motors.

In the present instance, the main armature Alis connected to an intermediate tap-point 210 of the non-corresponding field winding F2, and the other main armature A2 is connected to an intermediate tap-point 211 of the non-corresponding field winding F1. A single resistorR3 in the common negative conductor leading to ground is substituted for the parallel-connected resistors. R1 and R2 of'Fig. 6'.

As indicated by the various arrows, the effect of the two sections of each main field winding is cumulative and, therefore, the positive compounding action of the regenerated and exciting armature currents in the main field windings will counteract, to any desired degree, the negative compounding efl'ect of'the main-circuit resistor R3; F urthermore, the above-described load-balancing effect is again produced by the inter .connection of non-corresponding main armatures and field windings.

Moreover, if the design of parts is such that the upper or regenerated-current-excited sections 212 and 213 of the main field windings are adapted to produce the greater portion of the necessary excitation, the exciting current furnished to the other main-field-winding portions may be relatively small, with a resultant reduction in the initial cost and in the maintenance expense of the auxiliary motor-generator set.

Referring to Fig. 8, the main-field-winding circuits are established from one terminal of the exciting armature 11 through two similar parallel-connected circuits, one of which includes the main-circuit resistor R1,

the -main field windin F1 and a variable resistor R4, and the ot er of which includes main-circuit resistor R2, main field winding F2 and a variable resistor R5, common circuit being completed from the junctionpoint of the resistors R4 and R5 through a series-related field winding 183 for the exciting armature 11 to the negative terminal thereof.

The main-armature circuits are established from the trolley to a junction-point 214., where the circuit divides, one branch including a series-related field winding 178 for the auxiliary motor armature 10, the main armature A1 and the main resistor R1, and the other branch including a similar field winding 179 that is connected in series relation with the main armature A2 and the main resistor R2. The auxiliary motor armature 10 is also provided with the series-related field winding 13 which is differentially related to the regenerated-current-excited field windings 178 and 179.

The above-mentioned negative compounding effect that is produced by the main-circuit resistors R1 and R2 is counteracted to any desired extent in the following manner: Assuming an incipient increase of regenerated current in the main armature A1, for example, the corresponding increase of current traversing the field winding 178 for the auxiliary motor armature 10 causes a decrease of the total effective flux threading the armature, by reason of the differential relation of the field windings 178 and 13, whereby the motor-generator set speeds up to produce an increased voltage across the terminals of the exciting armature 11 to thus secure the desired imparting of a relatively fiat speed-torque curve to the main machines jointly. It will be understood, without further description, that a corresponding action takes place through the agency of the auxiliary field winding 179 when the current traversing the main armature A2 increases and, in either case, a converse action occurs upon an incipient decrease of main-armature current.

In Fig. 9, the main-circuit resistors R1 and R2 occupy the same respective positions relative to the main field windings F1 and F2, but the main armatures A1 and A2 are connected to the outer terminals of the noncorresponding resistors and, consequently, to the upper terminals of thenon-corresponding main field windings, whereby the resistors R1 and R2 carry a current equal to the difference between the corresponding regenerated current and the main-fieldwinding or exciting current, as indicated by the arrows.

The main circuit is established from the trolley through two similar parallel circuits, one branch including conductor 220, main armature A1, conductor 221, main resistor R2, and junction-point 222, and the other branch including conductor 223, main armature A2, conductor 224, main resistor R1 and the junction-point 222, whence a common circuit is completed through conductor 225, the auxiliary exciting armature 11, conductor 226, field winding 185 for the exciting armature and conductor 227 to the negative supply-circuit conductor Ground.

In the present instance, the exciting armature 1.1 is also provided with a shunt-excited field winding 184 that is difi'erential to the field winding 185, as indicated by the plus and minus signs, and the auxiliary motor armature 10 has a shunt-excited field windin 176.

y reason of the circuit connection just traced, and as indicated by the various arrows, the resistors'Rl and R2 exert a positive comipounding efi'ect rather than the negative compounding effect previously described, that is to say, any increase of regenerated current reduces the effective voltage drop, and the corresponding main-fieldwinding voltage is accordingly increased. The converse action occurs in case of an incipient decrease of main-armature current. However, the regenerated-current-excited field winding 185 for the exciting armature 11 is designed to produce a negative or opposing compounding effect upon the exciting armature, which effect is preferably slightl greater than the positive compounding e fect produced by the main-circuit resistors. Thus, the final result is similar to that obtained by the use of the previously described systems, although the function of the main resistors and the exciting-armature field winding have been interchanged.

The system shown in Fig. 10 comprises the main dynamo-electric machines having the armatures A1 and A2 and sub-divided field windings F1 and F2 together with a common main-circuit resistor R3, and a motorgenerator set having the series-compensating field winding 175, the shunt-excited field winding 17 6 for the auxiliary motor armature 10 and the supply-cirouit-excited field winding 15 for the auxiliary generator armature 11. In the present instance, the resistor R3 and the upper portions 212 and 213 of the main field windings carry a current equal to the difference between the exciting current and the regenerated current, as indicated by the various arrows. As described in connection with Fig. 9, the re sistor R3 produces a positive effect, while' the upper field winding sections 212 and 213 cause a somewhat larger negative compounding efi'ect.

Furthermore, the field winding portions 212 and 213 tend to maintain an even distribution of load between the main machines, since an increased current in the armature A1, for example, and, therefore, in the field winding section 212, causes a diminution of the effective field flux emitted by the cone sponding field winding F2, whereby the current traversing the armature A1 is caused to subside and the other machine absorbs additional load corresponding to the reduction of load upon the armature A1.

In Fig. 11, the main armatures A1 and A2 are connected to the lower terminals of the non-corresponding field windings F2 and F1, while the common main-circuit resistor R3 is connected in the same osition as that shown in Fig. 10. The varia 1e resistors R4 .and R5 are again connected to the lower terminals of the main field windings F1 and F2, respectively.

The auxiliary motor-generator set is shown as providedwith the field windings 176 and 15 for the auxiliary-motor armature 10 and generator armature 11, respectively.

One main circuit is established from the trolley throu h conductor 230, main armature A1, con uctor 231, whichis connected to the lower terminal 232 of the field winding F2, and thence, through the main field winding F2 and conductor 233, to junction-- point 234. A second main circuit is completed from the trolley through conductor 235, main armature A2, conductor 236, which is connected to the lower terminal 23? of the main field winding Fl, whence circuit is continued through the field winding and conductor 238 to the junction-point 234, a'

common circuit being completed through the resistor R3 and conductors 239 and 240 to ground.

' circuit is completed through conductor 247 to the opposite terminal of the exciting armature 11.

Under conditions of regenerative operation, the main-armature or regenerated current traverses the resistor R3 and also trav-' erses the main field windings, which produce a relatively strong positive compounding effect. However, the value of the resistor R3 is selected to produce a negative compounding action which slightly more than neutralizes the positive compounding effect of thefield windings, whereby the desired regenerative regulating operation is secured. Furthermore, the OI'OSS-COIIIIBOUOII of the main armatures and field windings tends to secure an even distribution of regenerated current, in the manner previously described.

I do not wish to be restricted to the specific circuit connections or arrangement of parts herein set forth, as various modifications thereof may be effected without departing from the spirit and scope of my invention. I desire, therefore, that only such limitations shall be imposed as are indicated in the appended claims.

I claim as my invention 1. In a system of regenerative control, the combination with a plurality of momentumdriven dynamo-electric machines, of means for imparting a predetermined compounding effect to the machines individually, and ot er single means for imparting an opposing compounding effect to the machines jointlly.

2. n a system of regenerative control, the combination with a plurality of momentumdriven dynamo-electric machines, of means for imparting a predetermined compounding elfect of one type tothe machines individually, and other single means for imparting acompoundirigelfect of the opposite type and of a different degree to the machines jointly.

3. In a system of regenerative control, the combination with a plurality of momentumdriven dynamo-electric machines, of means. for imparting a negative compounding effeet to the machines individually, and other single means for impartin a positive compounding effect to the mac ines jointly.

'4. In a system of regenerative control, the combination with a plurality of momentumdriven dynamo-electric machines, of an exciter system embodying means for impart ing a predetermined compounding effect to the machines individually and for imparting an opposing compounding efiect to the machines jointly. I

'1 5. In asystem of regenerative control, the combination with a plurality of momentumdriven dynamo-electric machines. or an exciter system embodying means for 1mparting a predetermined compounding eifect of one type to the machines individually and for imparting a compounding ,efl'ect of the opposite type and of a different degree to the machines jointly.

6. In a system of regenerative control, the combination with a plurality of momentumdriven dynamdelectric machines, of an exciter system embodying means for imparting a negative compounding effect to the machines individually and a lesser positive compounding effect to the machines jointly.

7 In a system of regenerative control, the combination with a plurality of momentumdriven dynamo-electric machines, of means for elfectlng olnt operation of said machines in accordance with a relatively fiat speed-torque curve, means for preventing sudden variations of regenerated current, and relay means for normally maintaining the regenerated current within predetermined limits.

8. In a system of regenerative control, the combination with a plurality of momentumdriven dynamo-electric machines, of-exciter means for effecting joint operation of said machines in accordance with a relatively flat speed-torque curve, resistor means for preventing sudden variations of regenerated current, a motor-type relay having its armature and field winding so energized as to maintain'regenerative action within predetermined limits, and means for manually adjusting the armature current of said relay.

9. In a system of regenerative control, the combination with a momentum-driven dynamo-electric machine, of a plurality of relay devices for normally maintaining the regenerated current within predetermined limits, andmeans dependent upon an interrupt-ion of the regenerative current for maintaining the generated Voltage within predetermined limits.

10. In a system of regenerative control,

the combination with a momentum-driven.

dynamo-electric machine, of a plurality of motor-type relay devlces having their armatures and field windings so energized as vto normally maintain the regenerated currality of solenoid-type relays for thereupon maintaining the generated voltage within predetermined limits until the resumption of supply-circuit voltage.

12. In a system of regenerative control, the combination with a momentun'i-driven dynamo-electric machine, of means for normally maintaining the regenerated current within predetermined limits, and means de pendent upon an interruption of the regenerative current for maintaining the generated voltage within predetermined limits.

13. In a system of regenerative control, the combination with a supply circuit and a momentum'driven dynamo-electric machine, of a controller for governing the excitation of the machine, a plurality of torque-relay means dependent upon the regenerated current for correctively actuating said controller to maintain such current within predetermined limits, means for rendering said torque-relay means inoperative upon an interruption of supply-circuit voltage, and a plurality of relay devices dependent upon the generated machine voltage for thereupon correctively actuating said controller to maintain such voltage within predetermined limits.

In testimony whereof, I have hereunto sub szcribed my name this 22nd day of March 191 RUDOLF E. HELLMUND. 

